In a surveying operation, including setting out, alignment, control in precise construction, machine assembly, and laboratory investigations, it is necessary that the precise height of a surveying instrument above a given surface be known. Such surveying instruments typically include theodolites, target plates, etc. Manual type height measurements are generally accomplished after a particular instrument has been mounted in an instrument engaging support member (tribrach) carried on a supporting member, such as a tripod. Typically, after each instrument has been mounted and aligned, a measurement of the distance between the instrument and ground is taken for the particular instrument so mounted since such distance of a given point of each particular instrument and ground may vary considerably.
The device of the present invention provides a measurement device which will permit a tripod having an instrument support, or tribrach, carried thereon to be set up and directly measured one time during the set-up operation. The direct measurement device is then removed, and any of a plurality of surveying instruments may be successively mounted and replaced on the tribrach.